This invention belongs to the field of agricultural chemistry, and provides to the art a new method of reducing the vigor of unwanted herbaceous plants. The growth of plants out of place has well-known deleterious effects on crops which are infested with such plants. Unwanted plants growing in cropland, as well as in fallow land, consume soil nutrients and water. Thus, such plants constitute a serious drain on the resources of the soil, and also shade crop plants from the sun.
The compounds of this invention are new to organic chemistry, although some pyridazinones have been disclosed before. For example, Breslow et al., "Diphenylcyclopropenone", J. Am. Chem. Soc. 87, 1321-25 (1965), and Izzo et al., "Reaction of Diazomethane with Cyclopropenones", Chem. & Ind. 839-40 (1964), disclosed processes for making 3,5-diphenyl-4(1H)-pyridazinone. This compound, without a 1-alkyl substituent, is not a useful herbicide.
Some pyridazinones have found use in agricultural chemistry. For example, 4-chloro-5-methylamino-2-(.alpha.,.alpha.,.alpha.-trifluoro-m-tolyl)-3(2H) -pyridazinone is a marketed herbicide. U.S. Pat. No. 3,644,355. East German Pat. No. 105,446 disclosed 1-phenyl-6-pyridazinones having halogen or amino substituents at the 4- and 5-positions which were said to be selective herbicides.